Heavy water is

Options

A. `H_(2)O`
B. `D_(2)O`
C. water at `4^(@)C`
D. water obtained by repeated distillation

Answer

**Step-by-Step Solution:**

1. **Understanding Heavy Water**: Heavy water is chemically known as deuterium oxide. It is represented by the formula D2O, where D stands for deuterium, an isotope of hydrogen.

2. **Composition of Heavy Water**: In heavy water, instead of the usual hydrogen atoms (H) found in regular water (H2O), there are two deuterium atoms (D). This makes heavy water denser than ordinary water.

3. **Occurrence of Heavy Water**: Heavy water is not found in large quantities in nature. It occurs in ordinary water in very small amounts, approximately 1 part in 6,000 parts of regular water.

4. **Production of Heavy Water**: Heavy water can be produced on a large scale through methods such as:
- **Electrolysis**: Repeated electrolysis of ordinary water containing an alkali can concentrate deuterium and produce heavy water.
- **Distillation**: Repeated distillation and condensation of water can also separate heavy water from ordinary water.

5. **Identifying the Correct Option**: Given the options, the correct answer is D2O, which is the chemical formula for heavy water. The other options (H2O, water at 4 degrees Celsius, and water obtained by repeated distillation) do not correctly represent heavy water.

**Final Answer**: Heavy water is D2O (deuterium oxide).

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